Nowadays, there are many kinds of numerical control systems, different forms, and their structure has their own characteristics. These structural features are derived from the basic requirements of the initial design of the system and the thought of the engineering design. For example, there are very different requirements for the point position control system and the continuous trajectory control system. There is also a great difference between T system and M system. The former is suitable for machining revolving parts, and the latter is suitable for machining parts with special shape and non revolving body. For different manufacturers, based on historical development factors and their own complicated factors, they may have different design ideas. For example, the Dynapath system uses small structure, convenient replacement and flexible combination of the board, while the FANUC system is the trend of the board structure, in favor of the reliability of the system, the system average failure rate was increased. However, no matter which system, their basic principles and composition are very similar. Generally, the whole CNC system consists of three parts, that is, the control system, the servo system and the position measurement system. The control system performs interpolation operation according to the workpiece program, and sends control instructions to servo drive system. The servo drive system amplifies the control instruction, drives the machine according to the requirements by servo motor, and the measuring system detects the movement position of the machine.

Or speed, and feedback to the control system to correct the control instructions. These three parts are organically combined to form a complete closed loop controlled CNC system.

The control system is mainly composed of bus, CPU, power, memory, operation panel and display, position control unit, PLC logic control unit and data input / output interface. The latest generation of CNC systems also includes a communication unit that can complete the internal data communication of CNC, PLC and the connection of the external high network. The servo drive system mainly includes the servo drive device and the motor. The position measuring system is mainly an incremental displacement encoder using a long grating or a circular grating.